Problem: Express your answer in scientific notation. $0.00045 - 2.5\cdot10^{-5} = $
Answer: $\phantom{=} {0.00045} - 2.5\cdot10^{-5} $ $={4.5 \cdot 10^{-4}} - 2.5 \cdot10^{-5} $ $={45 \cdot 10^{-5}} - 2.5 \cdot10^{-5} $ $= (45-2.5)\cdot10^{-5}$ $= 42.5\cdot10^{-5}$ $=4.25\cdot10^{-4}$